1. Field of the Invention
The field of art to which this invention pertains may be generally located in the class of devices relating to workpiece holding collets. Class 279 Chucks or Sockets, United States Patent Office Classification, appears to be the applicable general area of art to which the subject matter similar to this invention has been classified in the past.
2. Description of the Prior Art
This invention relates to collet mechanisms used in the machining, inspection and grinding industry, where high accuracy workpiece holding devices are required. U.S. Pat. Nos. 3,434,730 and 4,432,559 are illustrative of the prior art collet mechanisms which employ a plurality of flexible fingers mounted on a support sleeve, and which flexible fingers are adapted to be laterally spaced apart and around the outer periphery of a cylindrical workpiece. The prior art collet fingers are adapted to be cammed or compressed radially inward, into gripping engagement with the peripheral surface of a workpiece. A disadvantage of the prior art collet mechanisms employing flexible gripping fingers is that they do not provide a complete 360 degree gripping engagement with the circumference of a cylindrical workpiece. The lack of a 360 degree gripping engagement ability of the prior art collet mechanisms limits the use thereof for gripping a thin walled tubular workpiece close to an end thereof, without causing deflection of the workpiece. Other disadvantages of the prior art collet mechanisms that employ finger members, that are radially expanded and contracted, is that they are inefficient relative to concentricity and repeatability functions for gripping a workpiece, they are true at only one size, and the collet fingers have very minimal travel radially inward, as for example, seven or eight thousandths of an inch.